Summary: 1 | P a g e
The History of O
Life as we know it depends on the presence of oxygen in Earth's atmosphere. Today
there is 21%, but scientists believe that in the early history of the planet there was virtually
none. The breathing gas largely accumulated by the action of microbes that captured light
energy from the sun and harnessed it to both fix carbon dioxide into sugar and to split water ­
thus releasing oxygen gas to the air.
While these photosynthetic basics are known and widely accepted, charting the history
of oxygen in the atmosphere has until recently been mere guesswork. But, by collecting
thousands of wellpreserved samples from ancient sediments around the world and using
sophisticated instrumentation in the UM Geology Department, geochemists James Farquhar
and Jay Kaufman have revealed discrete pulses of oxygen at the beginning and end of the
Proterozoic Eon ­ that is, around 2,350 and 550 million years ago.
According to Kaufman and Farquhar, at these times atmospheric oxygenation had a
profound impact on the land, on the oceans, and on life. Their research suggests that variations
in the abundance of the breathing gas in the early Proterozoic atmosphere may also be related
to extreme climate change ­ insofar as the timing of oxygen rise immediately preceded a series
of worldwide ice ages. In the late Proterozoic, they suggest that the rise of oxygen may now
be directly linked to the evolution and diversification of higher plants and animals. Reports of
these spectacular findings have recently been published in high profile magazines including